color of candlestick lines

the line of a candlestick should have the same color as the body (rectangle)
EHN: add a span_stays option to widget.SpanSelector

If true, the selected span stays visible.
use GridSpec in plt.subplots

Use a GridSpec object to set up the subplots in plt.subplots.  Add an
optional parameter gridspec_kw.  This enables the user to specify
height_ratios and width_ratios to get grids with unequal row/column
sizes while still having the convenience that subplots provides.
Update widgets.py

removed whitespace
Deprecated matplotlib.testing.image_util.
Removed commented-out portions
Fixed LogFormatterExponent to correctly format negative exponents and added tests
Make LogFormatterExponent tests check more non-integer ticks and bases
Added missing cleanup decorator import.
PEP8 fixes for LogFormatterExponent
Merge pull request #2718 from ajdawson/animation-test-fail

Added missing cleanup decorator import.
Merge pull request #2691 from joferkington/fix-LogFormatterExponent

Change LogFormatterExponent to consistently format negative exponents
Merge pull request #2714 from pelson/deprecate_testing.image_util

Deprecated matplotlib.testing.image_util.
DOC : fixes small typos in matplotlib.dates docs

 - added explicit import for day of week alias
 - fixed dateutils -> dateutil type

closes issue #2724
Merge pull request #2725 from tacaswell/dates_doc_update

DOC : fixes small typos in matplotlib.dates docs
Merge pull request #2647 from rwirth/subplots_gridspec

use GridSpec in plt.subplots
Merge pull request #2595 from Tillsten/patch-1

EHN: add a span_stays option to widget.SpanSelector
Merge pull request #2207 from profholzer/patch-1

color of candlestick lines
use matplotlib._get_configdir() rather than manually setting path to config dir
Merge branch 'master' of github.com:matplotlib/matplotlib into styles_XDG_compliance